Quote from kidznurse
bottem line always has to be how safe are the patients
To a point. The sad truth is that there are managers who will hold that over their employees' heads, in effect, taking the patients hostage. "You have to come in or the patients will be the ones to suffer." If they are that concerned, let them pick up a shift now and then.
I agree with Ilg. If it's a short term problem caused by illness or some other unforeseeable calamity and you want to step up, feel free. If this is an ongoing situation because of insufficient staff, poor planning, and lack of incentives, don't feel any obligation to throw yourself into a gap that management should be filling by hiring more people, using in-house pool, contracting with agencies, or providing decent compensation for those who take on extra hours.
Agree to help out now and then, if you choose and are able. Do not agree to be exploited.